ANN ARBOR, MI - U.S. Rep. Debbie Dingell says the federal government's decision to take a closer look at the chemical 1,4-dioxane and its risks to human health and the environment is a significant step in the right direction.

"EPA's decision to conduct a risk evaluation of 1,4-dioxane for potential hazards to human health and the environment is critical for the 12th District of Michigan," Dingell said in a statement. "The growing dioxane plume that has been spreading through Ann Arbor's groundwater for decades poses a potential threat to our families and the community, and this announcement from EPA will help give us new tools to deal with this decades-old problem."

At this point, it remains unclear what will come of the evaluation. The TSCA, as amended by the Frank R. Lautenberg Chemical Safety for the 21st Century Act, required the EPA to publish a list of the first 10 chemicals it will evaluate.

When the list is published in the Federal Register, it will trigger a statutory deadline to complete risk evaluations for the chemicals within three years.

The evaluations will determine whether the chemicals present an unreasonable risk to humans and the environment.

If it is determined that a chemical presents an unreasonable risk, the EPA must mitigate that risk within two years.

Dingell, D-Dearborn, said TSCA reform was one of the few bipartisan accomplishments in Congress this year.

"Under the new reforms, 1,4-dioxane and thousands of other potentially hazardous chemicals will be reviewed for impacts on health and the environment on a priority basis," she said. "It is very significant that 1,4-dioxane is among the first 10 chemicals that EPA chose to evaluate and speaks to the importance of this work."

Dioxane, which is found in some consumer products, is classified by the EPA as likely to be carcinogenic to humans by all routes of exposure. It also can cause kidney and liver damage, and respiratory problems.

Local officials and citizen activists spent years pressuring the Michigan Department of Environmental Quality to lower the state's allowable level of dioxane in residential drinking water from 85 ppb to somewhere in the single digits. The DEQ recently acknowledged the 85 ppb was outdated and not protective of public health and lowered the exposure standard to 7.2 ppb.

The EPA published findings in 2010 suggesting dioxane at 3.5 ppb in drinking water poses a 1 in 100,000 cancer risk. Unfortunately, local officials say, that's merely a guideline and not a rule states have to follow.

"Unfortunately, there is currently no EPA maximum contaminant level for dioxane in drinking water," Kristen Schweighoefer, Washtenaw County's environmental health director, said in an email earlier this year. "The EPA's Integrated Risk Information System (IRIS) 3.5 ppb number we keep hearing about is not a maximum contaminant level. It is an estimated risk level of 1 in 100,000 of cancer cases of drinking water at 3.5 ppb dioxane. States are left to adopt their own standards for dioxane, and these standards vary across the country."

The dioxane plume in Ann Arbor was discovered in the 1980s and determined to be coming from the Gelman Sciences property on Wagner Road.

The plant manufactured filter devices and used dioxane as a solvent. It is estimated that 850,000 pounds of dioxane were used between 1966 and 1986, with most being discharged to soil, surface water and groundwater through seepage lagoons, land spray irrigation, and direct discharges at the site.

The Gelman dioxane plume has been the focus of much attention lately, including new legal action being taken by the city of Ann Arbor in Circuit Court, a petition to the EPA from two townships and the Sierra Club seeking a federal Superfund cleanup, and new emergency rules established by the state of Michigan following the discovery of dioxane in shallow groundwater under a park on Ann Arbor's west side. Dingell also has raised the issue with the EPA.

"We will continue to monitor this effort by EPA to ensure families in Michigan and across the country are protected from this toxic chemical," Dingell said of the upcoming evaluation of dioxane, which could take up to a few years. "In the short term, a petition to declare the Gelman dioxane plume a federal superfund site has been submitted to the EPA and we will continue to work with local officials to move that request forward. We will work with all stakeholders to ensure this contamination is properly remediated and the health of our families is protected."

Another chemical on the EPA's new list, tetrachloroethylene, is the focus of tests being conducted by the EPA in Ann Arbor. The agency is testing the air inside homes around Armen Cleaners, 630 S. Ashley St., to see see if toxic vapors from pollution in the ground are getting into people's homes at unsafe levels.